Use of lasers in industrial manufacturing environments has become widespread in recent years. Industrial uses of lasers include cutting and welding. In many instances, laser welding can replace resistance spot weld or MIG weld applications while providing greater flexibility and speed.
The use of a laser to weld sheet metal parts has presented some complicated obstacles. Typically, laser welding of sheet metal parts requires welding along seams one or more inches in length. When perfectly controlled surfaces are provided on sheet metal parts, laser welding of these seams has been done fairly easily. However, in more practical circumstances the surfaces of the sheet metal at the seams are not perfectly controlled. For example, there may be gaps at the seams where the two pieces of metal come together due to metal burrs, slight bends in the metal, etc. These gaps may range from 0 to 0.010 inches while a quality laser weld is maintained. However, gaps in the two pieces of metal in excess of 0.010 inches cause unsatisfactory welds and/or complete failure of the weld, rendering many sheet metal welding applications impractical.
When laser welding galvanized steel, the zinc coating of the steel vaporizes at a temperature at which the steel is still molten. This vaporization of the zinc can add to the formation of a laser beam blocking plasma barrier and can cause a porous weld. Known methods to address the vaporization of zinc include providing a painted on layer comprising a material that reacts with zinc or providing a high pressure gas barrier that prevents at least some of the zinc from boiling.
What is desired is a method for more effective laser welding of galvanized steel parts.